I have a ceramic diffuser, the nano ones off evilbay that can be had for 1-2 bucks a piece. I have that in the pump compartment wedged between the glass and the pump. Works very well. It does take an additional 20-30 minutes for the co2 to respond from when I had it in the display area, but looks better.
The up aqua 8/12 mm fits the stock spec tubing and can handle being submersed for a while. This is on my upgrade list.